[gggritso]

I wasn't aware of the photo-catalyst properties of bulk TiO2, so I'll have to agree with you there, but I'll say two things in defence of the article. Firstly, it does mention that a key factor in the effectiveness of TiO2 as a catalyst is the exposed surface area, so nano-sized TiO2 may be necessary to get the efficiency to make this viable. Perhaps bulk TiO2 just isn't enough. Secondly, nano-sized TiO2 responds to light differently (for example, I just did a lab experiment where TiO2 particles in nano behaved very differently under XRD from bulk TiO2). There might be other benefits that nano TiO2 offers that weren't mentioned in the article.

[zeteo]

Nano-size doesn't seem to play a crucial role in this application. The article is concerned with Italcementi's TX Active cement. Italcementi's main development is a photocatalytic hydraulic binder, and here's their patent:

https://data.epo.org/publication-server/getpdf.jsp?pn=094645...

In the patent, they claim that

"Any kind of photocatalyst able to oxidize in the presence of light, air and environmental humidity (oxygen and water) the polluting substances contacting the surface of the hydraulic binder (or the relative mortars and concretes) in a hardened state is part of the present invention, particularly a titanium dioxide, mainly in the form of anatase, or a precursor thereof, optionally doped with other atoms different from Ti."

[gggritso]

I glanced at the patent, and it looks like you're right. It doesn't say much about actual nano-properties at all.